Defrost fan rehab and rebuild thread (fresh air fan), or How the heck do if fix this thing? |
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Defrost fan rehab and rebuild thread (fresh air fan), or How the heck do if fix this thing? |
DRPHIL914 |
Jan 21 2021, 08:55 AM
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#1
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Dr. Phil Group: Members Posts: 5,766 Joined: 9-December 09 From: Bluffton, SC Member No.: 11,106 Region Association: South East States |
I have been dealing with this for 12 years, a non-running defrost fan. i even pulled this out 2 years ago and rebuilt it with new flapper seals and main body seal then made sure fan turned but didnt bench test the motor or resisitors, so as a result it still does not work properly. i will be documenting this because 914rubber and Mark will soon be putting together a kit for this that includes all the hardware seals and even a motor i believe, BUT i still have problems and questions!!! so i am starting this thread to get information on diagnosing the common causes of it not working and how to fix it, and then document the rebuild and replacement of the motor, fan, resistor and maybe the control unit in dash. Others have documented the reinstallation of the fan and the cables so i will not duplicate that. and we may want to link other threads hear that have done that as well.
Mark is sending me a kit soon, so while i wait for it, i will have to get some more information about the wiring and resistors function and how to test them . I had this out last week and tested 3 different control units due to thinking that my issue was a control issue, because it runs on one speed, #2, and anything else does not work and it will then throw the fuse. most assume this would be caused by bad slider unit but i tested 3 of them and 2 are like new with no wear on the sliders , still same result. so i am suspecting the resistors /plug aparatus . If anyone has done this and cares to share how to examine and test that for proper function, lets start there. Resistor function, which lead is which and examination of the control units I will take pictures of mine tonight and post those soon. once this figured out and fixed i will do a full step bystep on reassembly too. Looking for lots of help and input on this, thanks!!! Dr. Phil |
Superhawk996 |
Jan 28 2021, 06:59 AM
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#2
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914 Guru Group: Members Posts: 5,815 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
@DRPHIL914
Sure looks a lot better than 121 ohms on high and/or 0.8 ohms on all three which are were two of the sort of random conditions that you had on the other motor assembly. I'm wondering if you have some sort of resolution issue on you meter down at very low ohm setting. I have have serveral DMM's and a couple older analog multi-meters for special purposes. I have a cheap Sunpro DMM/Tach/Dwell meter that doesn't do well at low (sub 10 ohm) type work. Works great for Tach and dwell but I never trust it for resistance measurements. Out of curiosity, when you touch the test leads together do you get something very close to zero ohms . . . like maybe 0.1 or 0.2 ohms? Is it repeatable? The other thing that may be going on keeping high from showing lower resistance is the commutator may not be clean. I'd be curious if the resistance goes down after you run it on the bench for a few mintues and the brushes wipe across the commutator for a while. FYI -- in the process of destroying my fan motor, it was clear that the brushes in mine are non-serviceable. The only real reason after that for wanting to remove the impeller was to try to get some lubrication on the rear bushing that is largely obscured by the impeller. I'll find a better way on the new unit coming. I may order one of the fan motors from Pelican just so we can document how well those work and fit. Might be nice to have a brand spanking new motor. Probably will wait to see what shape this second fresh air box and blower is in that I just purchased as WTB before I pull the trigger on that idea. Interesting that the end of your motor appear to be capped over the bushings. Mine weren't. Either the design had changed or someone had previously pulled them off my motor long ago when the housing was 1st opened, clips broken, and it was molested. |
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